1. Field of the Invention
The present invention pertains to air bars for drying, and more particularly, pertains to an air bar with a rotatable slot nozzle for directional air flow control and diffusion.
2. Description of the Prior Art
Various coatings applied to webs in the production of products, such as photosensitive films, requrie drying of the coatings with circulating air. In many cases, the direct impingement of circulating air on the wet coating of the film resulted in undesired movement of the wet coating caused by blowing air on the coating surface before the coating had sufficiently set. The prior art drying systems required continual adjustment so as to avoid disturbances of the wet coating and including the reducing or eliminating of direct impingement of air, such as from air jets of an air bar, while the coating was wet and not set.
Prior art methods of drying wet coatings usually have not changed the direction of the impinging air. Dampered air nozzles of air bars reduced the jet velocity from the dampered air nozzles, but also reduced the total mass air flow in the dampered air bars. Other prior art system involved the retraction of the air bars from the web, but this proved ineffective, in that the distance of the air bars from the web increased and did not provide for a profiling air velocity within a given zone or over a given distance of the web. The effects of these techniques for a slot nozzle are discussed in "Heat Transfer Characteristics of Impinging Two Dimensional Air Jets", by Robert Gordon and J. Cahit Akfirat, Journal of Heat Transfer, February, 1966, at 101.
It has been difficult for the prior designs of drying systems to provide a match of an exact drying profile for a specific coating on a web, such as a photosensitive film over a prescribed distance of the dryer length.
The present invention overcomes the disadvantages of the prior art by providing an air bar with a rotatable slot nozzle assembly which can be rotated to change the direction of air flow from the rotatable slot nozzle.